Nevil Clavain is one of the oldest Conjoiners and can be credited with playing an overwhelming part in saving the human race from the Inhibitors. His actions throughout Redemption Ark set the scene for the evacuation of Resurgam and steers all factions of humanity towards stopping the Inhibitors. Born in the 22nd century, he originally fought against the Conjoiner faction as a senior military leader with the Coalition for Neural Purity. In that role, he had designed orbital lasers set above Mars, and led assaults on the Conjoiners on Mars, earning the epithet the Butcher of Tharsis. He is captured at one point and held prisoner by Galiana for months, but she treats him well and refrains from infiltrating his mind with nanobots, to his surprise; instead she tries to convince him of the Conjoiners' merits, and eventually releases him.
Nevil later visits the Conjoiners as an ambassador to try to come to a peace deal, but he and the Conjoiners are sabotaged by a large force led by Nevil's brother Warren. After being injured in battle, he awakens to find that Galiana has interfaced nanobots with his brain as the only way to save him, as his brother has faked his death. In order to escape Mars and the invasion by the forces of Neural Purity, he accepted the full Conjoiner implants to allow for the Conjoiners escape of Mars, which requires a rapid deceleration into Mars's moon, Phobos. After a non-specific time, Clavain leaves with the rest of the Conjoiners in the first relativistic interstellar spacecraft that can carry live human beings. Before leaving Mars, Clavain meets and befriends Remontoire, and the two remain close and loyal friends for centuries.
Centuries later, Clavain does not use the newer Conjoiner implant technology as Skade and other Conjoiners do and continues to rely on his outdated and old implants, which enables him to escape a growing threat from a secret infiltration from within the Conjoiners, by a sinister personality called the "Night Council" that has taken control of Skade. Clavain defects from the compromised Conjoiners with the intention of joining the Demarchists. Clavain departs from the Yellowstone system for the Resurgam system along with several other Conjoiners and Underworld figures from Chasm City.
Clashing in the Resurgam system, Clavain's allies manage to stall Skade long enough for the colony to be evacuated. After 23 years of relative peace after founding a colony on the Pattern Jugglers planet of Ararat, Clavain and Skade have their final encounter, where he accepts a deal with the dying Skade to allow a Caesarian section to be performed on her to recover the unborn Aura in exchange for the simultaneous torturing to the death of Clavain by the unwilling Scorpio. However, Clavain has the last laugh as he instructs Scorpio to bury him at sea, where the Pattern Jugglers absorb him and he is reunited with Galiana and Felka at last.